Dry and wet processes are known as the production of a metal sulfide for use in pigments and solid lubricants, such as tin sulfide, zinc sulfide and copper sulfide. Typically, the dry processes comprise reacting a metal with hydrogen sulfide or sulfur at high temperature under atmospheric or higher pressure, or reacting a metal compound and a sulfide such as thioamide in gas phase. Examples of known dry processes include a process comprising reacting highly-reactive metal powder with sulfur (please refer to Patent Document 1), and a process corresponding to the modification of the above-mentioned process that comprises reacting an agglomerate metal with sulfur while the agglomerate metal is milled (please refer to Patent Document 2). Another known dry process comprises reacting a metal chloride and thioacetamide or the like in gas phase (please refer to Patent Document 3).
On the other hand, the wet processes typically comprise reacting an aqueous solution of a metal compound with hydrogen sulfide, sodium hydrosulfide (sodium hydrogen sulfide) or the like. Examples of known wet processes include a process of reacting a metal alkoxide with hydrogen sulfide (please refer to Patent Document 4), a process of reacting a metal salt with sodium sulfide in water (please refer to Patent Document 5) and a process comprising reacting a metal salt with a thioamide such as thioacetamide (Patent Document 6).
To use a metal as raw material for the dry process, it is necessary to process metal ingot into metal powder. In the case of solid sulfur as raw material, powder sulfur should be used for the dry process. In general, powder metal sulfides are used in pigments and solid lubricants. However, most of metal sulfides that are thermally synthesized by the dry process are obtained as a sintered product, and are subjected to a milling step to produce a commercial product.
There is also disclosed a process in which sulfurization of metal is performed by generation of a pulsed electrical discharge plasma in sulfur (please refer to Patent Document 7).
Patent Document 1: JP 2002-511517 A
Patent Document 2: JP 2007-284309 A
Patent Document 3: JP 2004-091233 A
Patent Document 4: JP 06-293503 A
Patent Document 5: WO 2003/020848
Patent Document 6: JP 2004-520260 A
Patent Document 7: USSR No. 860428